Carbon measurement in aqueous samples using oxidation a elevated temperatures and pressures

ABSTRACT

Apparatus and methods for measuring the concentrations of organic and inorganic carbon, or of other materials, in aqueous samples are described, together with related, specially adapted components and sub-assemblies and related control, operational and monitoring systems.

FIELD OF THE INVENTION

This invention relates generally to methods and apparatus for makingvery precise, reliable and reproducible measurements of concentrationsof organic, inorganic and total carbon present in aqueous samples. Suchmethods and apparatus may be used, for example, to determine theconcentration of total organic carbon (TOC) in drinking water, rawwater, wastewater, industrial process streams and the like. Suchmeasurement may be utilized for various important commercial purposes,for example to optimize water purification processes, to detect spills,and to monitor compliance with environmental regulations. The methodsand apparatus of this invention can generally be applied both tomeasuring discrete aqueous samples, such as those encountered in alaboratory environment, and to monitoring flowing streams to providereal-time concentration data.

The apparatus of this invention is able to rapidly and accuratelymeasure carbon in samples containing high concentrations of salts andparticulate material because the sample is oxidized at high temperaturesand pressures, but is cooled to near ambient temperature before thesample exits the reactor. Since at least a portion of the sample leavesthe reactor in the liquid phase, salts and particulate material areswept from the reactor and do not accumulate there. The conditions ofthe oxidation result in efficient oxidation and accurate carbonmeasurements that cannot be achieved in oxidations initiated by UVradiation or in wet chemical oxidation at lower temperatures.Furthermore, samples that are highly contaminated, especially withparticulate material, are uniquely handled in the apparatus so that theydo not cause excessive wear of sample syringes, valves, or othercomponents, and do not settle out in the fluidic components. Bymaintaining the particulate material suspended in the liquid sample,plugging of fluidic components by particulates is minimized, and anyorganic material in those particulates is measured accurately.

BACKGROUND OF THE INVENTION

A. Overview

Total organic carbon is a well-established water quality parameter thatquantifies the overall concentration of organic substances, all of whichare typically regarded as contaminants, in an aqueous environment. Totalorganic carbon in an aqueous sample may be composed of either one or twocomponents—dissolved organic carbon (DOC) and particulate organiccarbon. The measurement of DOC is conventionally accomplished byfiltering the water sample, commonly through a 0.45-μm filter, to removeparticulate organic carbon prior to performing an analysis for DOC. Thelimitations of conventional apparatus and techniques for such analysisoften lead to the result that only DOC is effectively measured, insteadof TOC, because the particulates in a sample containing both forms oforganic carbon typically cause errors in the measurement and plug fluidpassages causing hardware failures.

In the following description, ‘DOC’ is used to refer to measurements inwhich the sample has first been filtered to remove particulates, while‘TOC’ is used herein to refer to measurements in which the sample hasnot been filtered. In other respects, however, the following descriptionis relevant to both DOC and TOC measurements.

In one known approach DOC and/or TOC, the organic compounds in anaqueous sample are oxidized to carbon dioxide (CO₂) and the CO₂ in thesample is then measured. In addition to organic carbon components, thewater sample may initially contain CO₂ and other inorganic forms ofcarbon (e.g., in the form of bicarbonate and carbonate salts). Together,these forms of inorganic carbon are referred to herein as IC. Totalcarbon (TC) concentration in an aqueous sample is therefore the sum ofthe TOC and IC concentrations.

Because an aqueous sample following an oxidation step could contain CO₂originating from both IC and TOC sources, the IC must be accounted forin some way to accurately measure TOC. One way to deal with IC is toremove the IC from the sample before the sample is oxidized. This iscommonly done by acidifying the sample to convert carbonates andbicarbonates into free CO₂, and then sparging it with CO₂-free gas toremove that CO₂ originating from IC sources. It has been found, however,that at least some volatile organic compounds may be removed from thesample during such a sparging step. Thus, when the sparged sample issubsequently oxidized, the CO₂ produced is from the oxidation of theremaining (non-purgeable) organics in the sample, so this measurement isoften referred to as the measurement of non-purgeable organic carbon(NPOC). Since many samples contain few, if any, purgeable organiccompounds, the concentration of NPOC in those samples is typicallyconsidered to be essentially equal to the TOC concentration.

A second way of dealing with IC in a sample is to separately measure theTC and IC concentrations. When using this approach, the TOCconcentration is calculated from the concentration difference, TC minusIC (TC−IC). One advantage of this approach is that the sample is notsparged so that purgeable organics are not lost thereby eliminating thissource of measurement errors. As a result, the measurement of TOC bythis “difference” approach is potentially more accurate.

When the approach to measuring carbon concentrations in aqueous samplesis not constrained by requirements for regulatory compliance, atechnician usually selects the parameter to be measured based on thetime and resources required for each measurement, and the expectedcomposition of the samples being monitored. Often, NPOC measurements areperformed because they are relatively fast. Where it is necessary toaccommodate a variable IC concentration, or where loss of purgeableorganic carbon results in too large a discrepancy to be tolerated, TOC(or DOC) is measured by the difference approach, as described above.

In other cases, the samples may either contain IC concentrations thatare known to be small compared to the TOC concentration, or the ICconcentrations are relatively constant. In such cases, a technician mayelect to measure TC because it is fast and it provides a sufficientlyaccurate indication of TOC trends for many common applications.

B. Identification of Related Prior Art

The following U.S. patents, each of which is incorporated herein byreference, are representative of pertinent prior art patents in thefield of this invention and in related technical areas, such asoxidation of organic wastes: U.S. Pat. Nos. 3,296,435 (Teal '435);3,700,891 (Luft '891); 3,958,945 (Takahashi '945); 4,619,902 (Bernard'902); 4,882,098 (Weetman '098); 4,896,971 (Weetman '971); 4,902,896(Fertig '896); 5,037,067 (Ray '067); 5,232,604 (Swallow '604); 5,271,900(Morita '900); 5,482,077 (Serafin '077); 5,630,444 (Callaghan '444);5,835,216 (Koskinen '216); 6,007,777 (Purcell '777); 6,114,700 (Blades'700); 6,142,458 (Howk '458); 6,375,900 B1 (Lee-Alvarez '900); and6,988,825 B2 (Colville '825).

The following technical publications, which are also incorporated hereinby reference, are also representative of the pertinent prior art in thisfield: Alken, G. R., “Chloride Interference in the Analysis of DissolvedOrganic Carbon by the Wet Oxidation Method,” Environ. Sci. Technol.,Vol. 26, No. 12, pp. 2435-2439; 1992; le Clercq, M.; van der Plicht, J.and Meijer, H. A. J., “A Supercritical Oxidation System for theDetermination of Carbon Isotope Ratios in Marine Dissolved OrganicCarbon,” Analyt. Chim. Acta, Vol. 370(1), pp. 19-27; 1998; Eyerer, P.,“TOC Measurements on the Basis of Supercritical Water Oxidation,”AE-2e.1; Fraunhover-Gesellschaft zur Foerderung, Institut ChemischeTechnologie; Munich, Germany,http://www.ict.fraunhofer.de/english/projects/meas/onlan/index.html#a5;ISO-CEN EN 1484, “Water Analysis Guidelines for the Determination ofTotal Organic Carbon (TOC) and Dissolved Organic Carbon (DOC),” 1997;Koprivnjak, J-F, et al., “The Underestimation of Concentrations ofDissolved Organic Carbon in Freshwaters,” Water Research, Vol. 29, No.1, pp. 91-94, 1995; Menzel, D. W. and Vaccaro, R. F., “The Measurementof Dissolved Organic and Particulate Carbon in Seawater,” Limnology andOceanography, Vol. 9(1), pp. 138-142, 1964; Nitta, M.; Iwata, T.; Sanui,Y. and Ogawachi, T., “Determination of Total Organic Carbon in HighlyPurified Water by Wet Oxidation at High Temperature and High Pressure,”presented at Tenth Annual Semiconductor Pure Water Conference; Feb.26-28, 1991, Santa Clara, Calif.; in Conference Proceedings, Balazs, M.K. (Ed.), pp. 314-320; Wangersky, P. J., “Dissolved Organic CarbonMethods: A Critical Review,” Marine Chem., Vol. 41, pp. 61-74, 1993;and, William, P. J. leB. et al., “DOC Subgroup Report,” Marine Chem.,Vol. 41, pp. 11-21, 1993. These patents and technical publications arefurther referred to in the following description.

C. Prior Art Related to Sample Handling and Sparging

Many prior art analyzers, such as those described in Morita '900,Purcell '777 and Lee-Alvarez '900, draw the sample into a syringe pump.Those syringe pumps use rotary valves to connect the syringe to thesample, reagents, dilution water and other analyzer apparatus. Any saltsand particulates in the sample contact the sealing surfaces of the valveand syringe. As particles settle onto those surfaces, they cause wearand premature leaking. Salts also dry on the surfaces and causeadditional wear because the salt crystals are abrasive.

Efficient sparging has been a goal of certain of the prior art patentsand publications. Takahashi '945, for example, describes a multi-stagesparger for use in TOC analyzers. Employing more than one stage improvesthe efficiency of the sparging process. However, the large internalvolume of this device would make it difficult to flush out between useswith different samples that have widely different concentrations ofcontaminants.

Weetman '098, Weetman '971, and Howk '458 teach that sparging can bemade more efficient by stirring the solution with rotating propellers.This modified sparging method would be complex to incorporate in ananalytical instrument, however, because of the motor and rotating sealsthat would be required.

In some prior carbon analyzers that add reagents to the sample, mixingis facilitated by bubbling gas through the solution (for example,Purcell '777). As discussed above, however, some samples should bemeasured without sparging because sparging can remove volatile organicsand thereby introduce an error into the measurements. However, noanalyzer is known to incorporate a device that can be used to spargecertain samples when desired, while also mixing other samples withreagents without sparging. Further, in prior analyzers, when thesparging stops, any particulates in the solution settle to the bottom ofthe sparger. This makes it impossible to accurately measure organicmaterial in the particles, and it increases the likelihood that fluidpassages of the apparatus will become plugged.

D. Prior Art Related to Oxidation Techniques

It is well known in the art to oxidize organic carbon using wet chemicalmethods. For example, in the Menzel and Vacarro publication, the authorsreport measuring DOC and particulate organic carbon in seawater byoxidizing a 5 mL sample in a sealed glass ampoule that also containedthe oxidizing agent potassium persulfate. The oxidation was achieved byheating the ampoule to 130° C. for 30 min. After the heating step, theampoule was cooled, broken open, and the CO₂ contained inside it wasmeasured using a non-dispersive infrared (NDIR) detector. Among otherdisadvantages, this method has the disadvantage that it involves manymanual steps. Furthermore, the ampoules can break when they are heatedor handled, raising concerns about loss of data and safety. This methodwould be impractical for real-time monitoring of process streams, oreven laboratory analyses where many samples are to be analyzed each day.

Bernard '902 describes an instrument that automates the wet chemicaloxidation method. The sample is acidified and a persulfate-containingreagent is added prior to the oxidation. CO₂-free gas is bubbled throughthe sample to remove the IC (in preparation for making an NPOCmeasurement) or to transfer it to a NDIR detector for measurement of theIC. The solution is then heated to 90 to 100° C. at ambient pressure toachieve oxidation of the organics. During the oxidation, the CO₂ istransferred to the NDIR detector where it is measured. The oxidation bypersulfate at these temperatures is slow; in fact, the innovative aspectof Bernard '902 is the use of metal catalysts to increase the rate ofthe oxidation.

Another shortcoming of such wet chemical methods is that the oxidationof organics by prior wet chemical methods is incomplete, especially whenthe sample contains chloride [as reported for example in thepublications of William, et al.; Wangersky; Koprivnjak, et al.; andAiken]. When the oxidation is incomplete, the TOC measurement isinaccurate because not all of the organic carbon is measured.

Purcell '777 describes another analytical instrument that measurescarbon in aqueous samples. In this case, the sample is acidified and anoxidizing reagent (a solution containing persulfate salts) is added tothe sample. This mixing occurs in a syringe, and the resulting solutionis then transferred to a sparger. After sparging, the syringe transfersthe sample to a reactor where the solution is irradiated withultraviolet (UV) radiation. In the presence of the UV radiation and thepersulfate reagent, many organics in the sample are oxidized to CO₂, andthe CO₂ is measured in a NDIR detector.

A problem with the oxidation of organics using UV radiation, as inPurcell '777, is that it is inefficient when the sample containsparticulates. For example, one study reported that TOC analyzers thatare based on UV oxidation detected less than 3% of the celluloseparticles added to samples at an actual concentration of 20 mg C/L. Bycomparison, analyzers based on high-temperature catalytic oxidation(HTCO), as described below, on average detected 83.2% of the celluloserepresented by cellulose particles.

To achieve more complete oxidation and, therefore, greater accuracy,analyzers were developed that oxidize organics using HTCO. Teal '435,for example, teaches that TOC in aqueous samples can be measured byinjecting a portion of an IC-free sample into a catalytic reactor heatedto around 900° C. The water vaporizes immediately, and organic materialsare oxidized to CO₂ upon contact with the catalyst. A carrier gas(oxygen) transports the CO₂ out of the reactor to a NDIR detector.

Morita '900 and Lee-Alvarez '900 describe methods and apparatus thatautomatically acidify and sparge samples, oxidize organics using HTCO,and use NDIR detectors to measure the CO₂. In both of these approaches,the sample is mixed with acid in a syringe connected to a multi-portvalve that directs fluids to other components. Morita '900 describes thesparging as being performed inside the syringe, while Lee-Alvarez '900describes a separate sparger.

A shortcoming of all methods based on HTCO is that samples containingsalts or particulate material will eventually plug the reactor becausethe water evaporates in the reactor, leaving nonvolatile salts andparticulates behind. In addition, the reactor typically requires twohours or more to cool enough so that it can be safely removed andcleaned. Then, about another two hours are required for the reactor toheat back up to its operating temperature. This means that theinstrument is out of service for an extended period whenever the reactormust be cleaned.

Other oxidation methods have also been reported. The Nitta et al.technical publication describes an analyzer in which the sample is mixedwith sulfuric acid and sodium persulfate. IC is removed by sparging, andthen a pump pressurizes a continuously flowing stream of the solution to2.0 to 2.5 MPa (284 to 356 psig). The pressurized solution is heated ina reactor to 200° C., and the organics are oxidized to CO₂. The solutionthen flows through a flow restrictor (it is the flow through thisrestrictor that generates the upstream pressure as stated above). TheCO₂ produced during the oxidation is removed by sparging and is measuredusing an infrared detector. Several Japanese patents describe additionalaspects of the instrument as described above (JP63135858, JP1021352,JP1021355, JP1021356, JP1021356, JP1049957, JP1049958, JP1318954,JP1318955, JP1318956, and JP5080022). This method has the advantage thathigher oxidation temperatures, presumably with more complete oxidation,can be achieved than if the oxidation were performed at ambientpressure. However, the apparatus has the disadvantage that particles andsalts will rapidly plug the restrictor. Furthermore, the cost of such anapparatus is likely to be high because solution has to be pumpedcontinuously against the backpressure generated by the restrictor.

Attempts to improve the efficiency of the oxidation also have includedoxidizing samples under supercritical conditions (i.e., above 374° C.and pressures above 22.12 MPa). Le Clercq et al. reported measuringcarbon isotope ratios in DOC. Between 500 and 1,000 mL of seawater weremixed with oxygen, pumped to a maximum pressure of 35 MPa, and forcedthrough an alumina reactor heated to 650° C. Placing a 0.18 mm IDcapillary downstream of the reactor and setting the flow rate at 2mL/min produced the aforementioned pressure. The gases exiting thecapillary were cooled to collect the CO₂ formed during the oxidation,and a mass spectrometer was used to measure the isotopes of carbon inthe CO₂. A problem with this apparatus is that samples that containparticulates tend to plug the capillary. Such a problem was reported byle Clercq et al., and they installed a 2-μm filter ahead of thecapillary in an attempt to mitigate the problem. However, inapplications in which the apparatus must operate for long periods, eventhe periodic plugging of such a filter would create excessivemaintenance and downtime. Another problem is the extremely hightemperature and pressure at which the oxidation is made to occur.Appropriate hardware for such operating conditions is costly, and it islikely to corrode rapidly. The reactor described in this technicalliterature was made from alumina to minimize corrosion, but thestructural characteristics of alumina make it unreliable. For thisreason, the alumina reactor had to be mounted inside a metal shield forsafety.

Eyerer reported another approach. The sample is first pumped through anelectrochemical cell that generates the oxidizing agent. Then the samplepasses through a reactor heated up to 600° C. and through a valve thatcreates a backpressure up to 26 MPa. The sample is oxidized at thoseconditions and then passes over a hydrophobic membrane. Some of the CO₂diffuses through the membrane and is measured in a mass spectrometer.This apparatus suffers from the same types of corrosion, reliability,and cost shortcomings, however, that were discussed above for the leClercq et al. approach.

Beyond applications in the measurement of organic carbon, as describedabove, rapid oxidation also has been a goal of developers of organicwaste destruction systems. One way of achieving the desired rapidoxidation rates has been to perform the oxidation at near-critical andsupercritical conditions. A variety of oxidizing agents have beenemployed, and one of the most economically attractive oxidizers is theoxygen in air. Swallow '604 teaches that if ozone, hydrogen peroxide, orsalts containing persulfate, permanganate, nitrate, and otheroxygen-containing anions are added to the liquid/air mixture, theoxidation rate is sufficiently rapid that the exothermic processoperates without supplemental heating. This is an importantconsideration for large industrial processes, but it is much lessimportant to analytical instrumentation because the hardware is muchsmaller.

Instead of oxidizing organics in a continuously flowing stream, batchesof the sample could be heated. To do that requires that the batch besealed in a container that is subsequently heated, and the best way ofautomatically sealing the container would be to use a valve that canwithstand the pressure generated during heating. Many valves designedfor high-pressure applications employ precision sealing surfaces. Ballvalves require highly polished balls in packing glands to avoid leaks.Other high-pressure valves require metal-to-metal seals (for example, asdescribed in Callaghan '444). Those valves are costly and subject torapid wear by particles in the liquid.

A better method of achieving valve sealing in the presence ofparticulates is to use a softer seal that is resistant to abrasion.Serafin '077 teaches that elastomeric seals can be used in check valvesat high pressure, and Ray '067 describes the use of O-rings to seal theports in a plug valve. Both inventions have the disadvantage that theseals are not easily accessed for replacement when they become worn.

E. Prior Art Related to NDIR Detectors

NDIR detectors of CO₂ used as components of TOC analyzers commonly use arotating chopper wheel to modulate the infrared (IR) radiation, and apneumatic IR detector to measure the IR radiation that has not beenabsorbed by the CO₂ being measured. Luft '891 describes such a NDIRdetector. Shortcomings of this technology include the fact that thechopper wheel mechanism is subject to failure, and irregularities in thesize and orientation of the openings in the chopper wheel producesignificant electrical noise in the measurement of CO₂.

To overcome the effects of temperature and pressure on NDIR response,detectors with built-in temperature and pressure compensation have beenreported, such as in Fertig '896. An alternative approach to overcomingtemperature effects is to use an IR detector that is relativelyunaffected by temperature, such as a pyroelectric detector. Koskinen'216 describes a NDIR detector that electronically modulates the IRsource to avoid problems with chopper wheels, and it uses a pyroelectricIR detector. However, this NDIR uses a costly Fabry-Perot interferometerto select the IR wavelength that is measured.

Blades '700 describes a NDIR detector designed specifically for use in aTOC analyzer. The IR source is an electrically modulated incandescentlamp with a pyroelectric IR detector. However, the use of anincandescent lamp limits the dynamic range and sensitivity of the NDIRbecause the modulation is limited to low frequencies.

Commonly, NDIR detectors use rectifier circuits and lowpass filters toproduce a DC signal that is proportional to the average output of the IRdetector. Shortcomings of this technology include the conversion of“noise” over a wide bandwidth into a part of the rectifier outputsignal. Additionally, the lowpass filter that averages the rectifiedwaveform also impairs the ability of the NDIR to respond to rapidlychanging CO₂ concentrations. Blades '700 reports an NDIR that uses twosynchronous detectors, with each responding to opposite half-cycles ofthe signal from the IR detector. The use of two synchronous detectorsimproves the response time limitation of the rectifier circuit, but thisapproach still suffers from the shortcoming of mixing noise into theoutput signal.

Carbon measurement instruments commonly generate chlorine when thesample contains chloride ions. That chlorine would corrode many NDIRdetectors, so scrubbers are used to remove the chlorine before it entersthe NDIR (as, for example, in Lee-Alvarez '900 and Purcell '777). Thescrubber is a consumable that adds to the operating cost and maintenancelabor of those instruments.

These and other limitations of, and deficiencies in, the prior artapproaches to IC, TOC and TC measurements are overcome in whole, or atleast in part, by the methods and apparatus of this invention.

OBJECTS OF THE INVENTION

Accordingly, a general object of this invention is to provide methodsand apparatus for determining the presence of and/or measuring one ormore other elements, other than hydrogen and oxygen, e.g., an impurity,that may be present in an aqueous sample when at least one of such otherelements may be present in organic form, inorganic form or both.

A more particular object of the present invention is to provide methodsand related apparatus, which may be readily automated, for determiningthe presence of and/or measuring organic and/or inorganic carbon in oneor a series of discrete aqueous samples.

Another principal object of the present invention is to provide methodsand related automated apparatus for measuring and/or monitoring theconcentrations of organic and/or inorganic carbon in one or more flowingaqueous streams.

Another object of this invention is to provide methods and relatedapparatus for measuring organic and inorganic carbon in one or a seriesof discrete aqueous samples and/or flowing streams that may containparticulates and salts.

Yet another object of this invention is to provide for the addition ofreagents and, when needed, dilution water to a sample being tested in away that particulates and salts in the sample do not plug fluid passagesor cause excessive wear to syringe pump components.

Still another object of this invention is to provide for the effectivetransfer of particulates in an aqueous sample being analyzed into asealable oxidation reactor in a substantially homogenous solution orsuspension, so that carbon concentration measurements accurately reflectthe amount of carbon in the particulate material.

Another object of this invention is to provide methods and relatedapparatus for oxidizing, reacting and/or decomposing organic material inan aqueous sample using a reactor that can be sealed while an aqueoussample inside the reactor is subjected to temperature and pressureconditions sufficient to cause oxidation, reaction and/or decompositionof the organic material in the sample.

A more specific object of this invention is to provide methods andrelated apparatus that oxidize the organic carbon in an aqueous samplesubstantially completely in a sealable reactor, so that the measurementsof organic carbon accurately reflect all of the carbon whether presentin dissolved and/or particulate form in the sample.

Yet another object of this invention is to provide methods and relatedapparatus that measure CO₂ derived from the organic and/or inorganiccarbon in an aqueous sample in a way that is reliable, reproducible andessentially unaffected by variations in temperature, pressure, orconcentrations of CO₂ in the ambient air.

Another object of this invention is to measure CO₂ derived from theorganic and/or inorganic carbon in an aqueous sample over a wide rangeof concentrations, while rejecting “noise” or interferences that wouldlimit CO₂ measurement accuracy at low concentrations and yet stillresponding quickly to rapid changes in the CO₂ concentration.

Still another object of this invention is to measure CO₂ derived fromthe organic and/or inorganic carbon in an aqueous sample whilesubstantially avoiding corrosion of the measurement apparatus bychlorine or other oxidation products emanating from an oxidation reactorused in the measurement method.

These and other objects and advantages of this invention will beapparent from the following detailed description with reference to theattached drawings.

SUMMARY OF THE INVENTION

By contrast with the limitations of the prior art approaches to makingsuch carbon concentration determinations in aqueous samples, asdiscussed above, the methods and apparatus of the present invention areuniquely capable of measuring all of the aforementioned parameters insamples that contain concentrations of TOC, dissolved solids, andparticulates. In general a sample is drawn into the analyzer of thisinvention, reagents are added, and the sample is diluted as necessary.With the present invention, it is possible to completely avoid havingthe sample enter apparatus components that would be damaged by thedissolved solids or particulates in the sample. This invention alsokeeps the particulates suspended in the sample solution at least untilit enters the oxidation reactor. This procedure therefore allowsparticulate organic carbon to be measured accurately, and it avoidsadditional maintenance labor and downtime that would otherwise be causedif particulates were allowed to settle out in the sparger and plugsample passages.

The oxidation of the organic carbon (or other organic material) in aknown volume of sample processed according to this invention occurs in areactor, which can alternately be sealed to contain a fluid therein atelevated temperature and pressure conditions or unsealed to introduce orremove a fluid sample. Such a sealable reactor is uniquely designed andadapted to be capable of handling samples that contain salts andparticulates. In a representative invention embodiment, a known volumeof sample is flowed into the sealable reactor, which initially is cool,through an open reactor inlet port. The reactor is then sealed and,after being sealed, is rapidly heated to temperature and pressureconditions at which the organic material in the sample is rapidlyoxidized. Because the water in the aqueous sample cannot boil away inthe sealed interior of the reactor, the sample (and the organic materialin the sample) can be heated to relatively high temperatures andpressures. Furthermore, it has been found that, at the hightemperature/pressure conditions attainable inside the sealed reactor ofthis invention, water in the aqueous sample can become a supercriticalfluid that exhibits special properties including properties thatfacilitate the rapid oxidation of organic material.

When the oxidation of organic material is complete, the reactor isquickly cooled to near ambient temperature so as to condense a liquidreactor product. The reactor is then opened, and the oxidized sampleexits the reactor through an open reactor outlet port in part as aliquid reactor product (taking with it the salts that were originallydissolved in it) together with a gaseous reactor product that willinclude organic material oxidation products such as CO₂. Particulatesalso are flushed out of the reactor. Because a liquid reactor product isrecovered in this step, the salts and particulates do not accumulate inthe reactor, and, as a result, maintenance and downtime are minimized.

The CO₂ in an oxidized sample coming from the reactor is measured in aninnovative type of NDIR detector according to this invention that isreliable, stable, and has a wide dynamic range. These characteristics ofthe NDIR detector of this invention allow the analyzer to operate forlong periods without recalibration.

The present invention has a particular advantage in that samples are notdrawn into a syringe or its valving, where salts and particulates wouldcause leaks. Instead, the sample and the reagents are drawn into alength of tubing by means of a syringe that itself contains only cleandilution water. That dilution water also can be used to dilute samplesthat contain very high concentrations of organic carbon prior to furtherprocessing. In a preferred embodiment of this invention, the analyzer iscapable of measuring up to about 1,000 ppm TOC in a sample withoutdilution of the sample, and up to about 50,000 ppm TOC in a sample ifthe sample is diluted (the only constraint here being the preferredsizes of the various apparatus components, with a larger apparatus beingcapable of handling even higher TOC concentrations with appropriatedilution).

The mixture or combination of sample and reagents (and dilution waterwhen necessary) then enter a mixing device according to this inventionthat can both mix and sparge the solution/suspension. The mixingapparatus consists of a solenoid and a magnetic stirrer (stirring bar)that is coated with an inert polymer to prevent corrosion. The stirringbar may have protrusions on each end that help to agitate the samplemixture as the bar moves up and down in the chamber. This designrequires no motors or rotating seals. The magnetic mixer of thisinvention has been found to unexpectedly improve the efficiency of thesparging when it is activated. Such an improvement is unexpected in viewof the fact that the gas bubbles by themselves seem to agitate thesolution vigorously during the sparging process. Less time is thereforerequired for essentially complete removal of IC when using themixing/sparging apparatus of this invention, thus making the analysisfaster.

Organic compounds are oxidized efficiently in a preferred embodiment ofthis invention at temperatures around 375° C. At this temperature, theoxidation of organics with persulfate, oxygen, or other oxidizers israpid and substantially complete. We have found that there is nocorrosion of the reactor and valves when they are constructed fromtitanium.

The reactor in the present invention is unusually reliable because it isheated only during the short period when a sample is actually beingoxidized. The preferred reactor of this invention has a relatively smallmass which allows it to be rapidly heated to oxidize the sample, andthen rapidly be cooled back down to ambient temperature. The presentinvention can be put into service rapidly upon initial startup or aftermaintenance, thereby minimizing downtime.

In a preferred embodiment of the invention, the special high-pressurevalves used at the inlet and outlet ports of the reactor tube includeseals constructed of high-density polyethylene, polyvinylidene fluoride(PVDF), or elastomers such as ethylene propylene diene monomer (EPDM).The use of these materials allows the valves to seal reliably even whenthe sample being processed contains particulate material, and the costof these valves is reduced because precision machining is not necessary.An unusual feature of the reactor valves according to this invention isthat the seals can be easily and quickly replaced when they do becomeworn. In addition, the reactor valves of this invention are unlike anyother known valves because each valve incorporates a bypass fluid paththat allows the interior of each of the valves to be flushed clean whenthe reactor is sealed.

The present invention does not require costly high-pressure pumps orrestrictors that would be plugged by particulates. It does not requirethe use of fragile ampoules, UV lamps that contain toxic mercury, orexpensive catalysts. The completeness of oxidation is not degraded bythe presence of chloride or particulate materials in the sample. UnlikeHTCO reactors of the prior art, the present invention does notaccumulate salts or particulates in the reactor, and maintenance on thereactor is minimal.

The NDIR detector according to the present invention is especiallyreliable because it has no moving parts, and it is constructed ofmaterials that are compatible with oxidation products coming from thereactor, including chlorine. Unlike many other comparable instruments,with this invention no scrubbers are required to remove chlorine fromthe gas entering the NDIR.

The IR source utilized in this invention can be selected from amongvarious types of infrared radiation sources, including incandescentlight bulbs, thermal radiators, and electroluminescent diodes. The IRsource in the preferred embodiment is a thin thermoresistive film thatproduces intense IR radiation, even when electrically modulated at highfrequencies that permit low concentrations of CO₂ to be measured withprecision.

The IR detector utilized in this invention can also be selected fromamong various types of infrared radiation detectors, includingbolometric, thermoelectric, and photoelectric types. The pyroelectric IRdetector in a preferred invention embodiment is one that is relativelyimmune to temperature changes. To further eliminate the effects oftemperature, the IR source and IR detector may be controlled at fixedtemperatures in a preferred embodiment. The IR source and IR detectorare preferably mounted in chambers that are flushed with CO₂-free gas,thereby preventing response variations due to changes in the ambient CO₂concentration. The response of the NDIR may also be adjusted tocompensate for changes in the pressure of the CO₂.

Multiple wavelengths can be used to measure CO₂ in the NDIR of thisinvention, and the selected wavelength can be implemented in any ofseveral ways, including the use of optical filters and the use of IRsources that emit radiation of the desired wavelengths (e.g.,light-emitting diodes). When optical filters are used, they can belocated in various locations within the NDIR detector. In a preferredembodiment, a nominal wavelength of about 4.26 μm is used for CO₂measurement, and the optical filter that is employed to eliminate otherwavelengths is part of the IR detector, and typically is locatedimmediately in front of its sensing element.

In one illustrative embodiment of this invention, a sample is drawn intothe instrument using a syringe pump. Instead of the sample entering thesyringe, however, the sample enters a length of tubing that can beeasily and inexpensively replaced if it ever becomes plugged orpermanently contaminated by a sample. The tubing is advantageouslycoiled to reduce the amount of space it occupies inside the instrument.

The syringe is also arranged and/or connected so as to sequentially (butin any desired order) draw acid and oxidizer reagents and sample intothe coil of tubing. If the concentration of the organic carbon in thesample is very large, dilution water can be drawn in, too, as discussedabove. The total volume of liquid drawn into the tubing is known bymonitoring the operation of the syringe pump, so dilution ratios can becontrolled precisely.

The several fluids in the coil tubing can then be discharged to a mixinglocation in the apparatus, such as a chamber that combines a mixer andsparger. The sample and other fluids in the mixing chamber can bethoroughly mixed and sparged to measure NPOC, or mixed without spargingwhen TC or IC is being measured. The mixing action keeps particulatessuspended substantially homogenously in solution or suspension, so thesolution/suspension can be accurately measured without plugging themixing chamber or the tubing connected to it.

A portion of the sample mixture from the mixing chamber is then flowedto a reactor tube of an oxidization reactor where it is sealed in aninterior region of the reactor tube. Reactor valves as described above,and able to withstand high pressures, seal each end of the reactor tube.The tube is then heated to temperatures between about 150° C. and 650°C., or preferably between about 300° C. and 400° C., and more preferablybetween about 350° C. and 390° C. The tube is heated for approximatelyone to thirty minutes, e.g., preferably for about two to four minutes.At the end of that period, the heater is turned off, and a fan blowsambient air over the reactor tube to rapidly cool it to near ambienttemperature. The valves are opened, and a CO₂-free carrier gas is usedto blow the reactor liquid and reactor gas from the interior region ofthe reactor tube. The liquid and gas reactor products are separated, andthe carrier gas transfers the gaseous oxidation products, including theCO₂, to a chemical detector, e.g., an NDIR detector, in accordance withthis invention for carbon measurement.

In the NDIR, IR radiation is emitted from an IR source that iselectrically modulated at a suitable frequency, in one preferredinvention embodiment at 55 Hz. In one preferred embodiment, the IRsource is maintained at a suitable fixed temperature (e.g., about 65°C.) in a chamber that is purged by CO₂-free gas. The IR radiation fromthe source is collimated by a lens and passes through the gas (acombination of the gaseous oxidation products and carrier gas) flowingfrom the reactor. Any CO₂ present in the gas flowing through the NDIRabsorbs IR at wavelengths around 4.26 μm, e.g., 4.26 μm±0.2 μm. The IRradiation that is not absorbed by CO₂ then passes through a second lensthat focuses it onto an IR detector. In one preferred embodiment, afilter is located on the face of this IR detector to block IR atwavelengths other than 4.26 μm from reaching the pyroelectric detectorelement, and the IR detector is mounted in a chamber that is purged withCO₂-free gas, and is maintained at a fixed temperature (e.g., about 55°C.).

The NDIR electronic circuitry drives the IR source at the modulationfrequency, and the IR detector converts the infrared light that itreceives back into an electrical signal, which signal is attenuated byany CO₂ present in the gas being measured. The NDIR electronic circuitryconditions this signal with a bandpass filter, and then converts thisanalog signal to digital with an analog-to-digital converter thatsamples the waveform many times per modulation cycle (in one preferredinvention embodiment, at 100 waveform samples per modulation cycle). TheNDIR electronic circuitry also uses digital signal processing techniquesto perform further bandpass filtering and to measure the amplitude ofthe received signal. From this amplitude, the NDIR electronic circuitrycalculates and reports the CO₂ concentration in the gas flowed from thereactor.

In a more specific apparatus embodiment, this invention comprises ananalytical instrument for measuring carbon in a liquid sample, whereinthe instrument comprises in combination: a sample inlet; a pump to drawsaid sample and, optionally, other materials into the apparatus; amixing chamber; a source of sparging and/or carrier gas and a gas flowcontrol system; an oxidation reactor, wherein the oxidation reactor canbe sealed at each end to contain a sample mixture; a heater; a fluidpumping system to transport liquids and mixtures of gases and liquidsthrough the aforementioned components; and a CO₂ detector to measure CO₂in the reactor product coming from the reactor.

In another specific embodiment, this invention comprises an analyticalinstrument having the several elements and components as describedabove, and further includes an acidic reagent inlet.

In another specific embodiment, this invention comprises an analyticalinstrument having the several elements and components as describedabove, and further includes an oxidizer reagent inlet.

In another specific embodiment, this invention comprises an analyticalinstrument having the several elements and components as describedabove, and further includes a dilution water inlet.

In still another specific embodiment, this invention comprises ananalytical instrument having the several elements and components asdescribed above, and further includes a fan or blower to cool thereactor.

In still another specific embodiment, this invention comprises ananalytical instrument having the several elements and components asdescribed above, and further includes a mixing or mixing/spargingchamber that is configured in a way that relatively easily permits asparging gas to be bubbled through a solution or liquid suspensioncontained in the mixing/sparging chamber.

In yet another specific embodiment, this invention comprises ananalytical instrument having the several elements and components asdescribed above, and further includes a valve or comparable flow controlelement for directing or channeling gas coming from the mixing/spargingchamber (after it has been bubbled through a solution or liquidsuspension, e.g., an acidified sample mixture, contained in the chamber)to the CO₂ detector.

In another specific embodiment, this invention comprises an analyticalinstrument having the several elements and components as describedabove, and further includes a NDIR detector designed to measure a widerange of CO₂ concentrations using AC signal processing for noiserejection/filtering and for signal amplitude measurements.

In another specific embodiment, this invention comprises automating ananalytical instrument having the several elements and components asdescribed above using electronic and/or computer control systems asherein described.

In another specific embodiment, this invention comprises methods ofoperating and controlling an analytical instrument having the severalelements and components as described above.

In a general method embodiment, a method according to this inventioncomprises the sequential steps of drawing a selected volume of sampleinto a sample-handling portion of the analytical system; adding suitablevolumes of an acid reagent (of a known acidity or acid concentration)and, depending on the type of carbon being measured, also of an oxidizerreagent (of a known concentration) relative to the volume of sample;possibly diluting the sample/acid/oxidizer mixture with low oressentially zero TOC dilution water if desired; mixing the sample, acid,oxidizer (if present) and dilution water (if any) to form asubstantially homogenous solution or liquid suspension; if NPOC is to bemeasured, sparging the acidified solution/suspension with CO₂-free gas(provided, for example, by a gas control assembly of the system) whilecontrolling the flow rate of the sparge gas to ensure that IC in thesample is substantially completely removed; alternatively, if TC or ICis to be measured, mixing but not sparging the solution/suspension;transferring a portion of the homogenous mixed/spargedsolution/suspension to an oxidation reactor; if NPOC or TC is to bemeasured, heating the portion of the solution/suspension after thereactor is sealed to oxidize organic compounds in the portion of thesolution/suspension, then cooling it to near room temperature; using astream of carrier gas from a gas control assembly to transfer the liquidand gaseous reactor products in the reactor to a gas/liquid separator;separating the liquid from the gas, and removing the separated liquidfrom the gas/liquid separator; flowing the gaseous reactor product(containing the CO₂) from the gas/liquid separator to an NDIR detector;measuring the CO₂ in the gaseous reactor product using the NDIRdetector; and, optionally, after the CO₂ in the gaseous reactor productis measured, flowing the gaseous reactor product back through thegas/liquid separator and then venting it to the atmosphere.

In another apparatus embodiment, an apparatus according to thisinvention comprises the following apparatus elements or components incombination: a sample-handling unit comprising multiple valves and asyringe connected through a three-way valve to both a coil of tubing anda reservoir containing low-TOC dilution water, wherein the internalvolume of the coil of tubing is larger than the internal volume of thesyringe; a pump to draw sample from a sample source and deliver it by aconduit connection to a six-way fluid interconnection element; amixing/sparging chamber connected to the coil of tubing, said chamberincluding a sparging element for sparging CO₂-free gas through asolution/suspension in the chamber; a source of compressed CO₂-free gasconnected to the sparging element and a gas control module to controlthe flow and pressure of such gas; optionally, a valve and conduit todirect gas emerging from the mixing/sparging chamber through agas/liquid separator and then to an NDIR detector; a pump and associatedconduit to transfer at least a portion of the mixed/spargedsolution/suspension from the mixing/sparging chamber to a sealablereactor; a source of carrier gas connected to the reactor and, via thegas/liquid separator, to an in-line filter and then to the NDIRdetector; a heater and a fan associated with the reactor; and anassociated automated control system comprising electrical connectionsand operational software adapted to operate fluid valves and othersystem control elements according to a predetermined sequence and/ortiming or, alternatively, in accordance with feedback received fromvarious system monitors.

In another specific apparatus embodiment, an NDIR detector in accordancewith this invention comprises three chambers: a first chamber containingan IR source; a second chamber centrally located and comprising anoptical path through which carrier gas and a gaseous reactor productincluding CO₂ flow; and a third chamber containing the IR detector,wherein said first and third chambers are designed to be flushed with aCO₂-free gas during measurements.

In another specific apparatus embodiment, a mixer/sparger element inaccordance with this invention comprises a top section that includes aliquid inlet and a sparge gas outlet, a bottom section that includes aninlet port for sparge gas and a liquid outlet, and a middle sectioncontaining a magnetic stirrer component, the middle section beinglocated inside a solenoid coil which can be activated by passing aseries of current pulses through it causing the magnetic stirrercomponent to move up and down inside the middle section.

In another specific apparatus embodiment, an apparatus, in accordancewith this invention comprises a pair of high-pressure reactor valves,each such valve comprising a polymeric or elastic seal attached to aplunger that moves back and forth inside a valve body when an associatedmotor is activated, and wherein the rear portion of the seal retains twoO-rings so as to seal the interior of the housing, and wherein the frontportion of that seal plugs a reactor opening (a reactor inlet or areactor outlet) when the valve is in a closed position.

In another specific apparatus embodiment, an IR source for the NDIR inaccordance with this invention comprises a modulated, thin-film IRradiator.

In another specific apparatus embodiment, an NDIR detector in accordancewith this invention comprises a pyroelectric sensor element, with thepreferred embodiment having a pyroelectric sensor constructed fromlithium tantalate.

Even more specifically, the present invention comprises the followingembodiments:

1. An analytical instrument comprising in combination: a liquid sampleinlet; a fluid transport system for drawing a known volume of a liquidsample into the instrument and for transporting liquids and gases to andthrough the components of the instrument; a reactor that can alternatelybe opened, to introduce a sample or to discharge a reactor product, orsealed to heat treat a sample inside the reactor to produce a reactorproduct; a reactor heating unit that can be turned on during a reactorheating cycle and turned off during a reactor cooling cycle; a reactorcooling unit that can be turned on during a reactor cooling cycle andturned off during a reactor heating cycle; a source of gas and a gasflow control system in communication with the fluid transport system;and, a chemical detector to measure a chemical component of the reactorproduct.

2. The instrument of paragraph 1 further comprising a fluid pumpingsystem in communication with the fluid transport system.

3. The instrument of paragraph 1 further comprising one or moreadditional inlets selected from an acid reagent inlet, an oxidizerreagent inlet and a dilution water inlet.

4. The instrument of paragraph 1 further comprising a mixing/spargingchamber upstream from the reactor where a combination of a liquid sampleand one or more other liquids can be either mixed or mixed andsimultaneously sparged with sparge gas.

5. The instrument of paragraph 1 wherein the chemical detector comprisesa detector for carbon, nitrogen or sulfur oxidation products downstreamof the reactor.

6. The instrument of paragraph 1 wherein the chemical detector comprisesa non-dispersive infrared (NDIR) detector downstream of the reactor.

7. The instrument of paragraph 6 wherein the NDIR includes an opticalfilter specific to the wavelength of IR radiation absorbed by thechemical component to be measured.

8. The instrument of paragraph 7 wherein the optical filter is specificto carbon oxidation products.

9. The instrument of paragraph 7 wherein the optical filter is specificto CO₂.

10. The instrument of paragraph 6 further comprising a gas/liquidseparator between the reactor and the NDIR detector to remove liquidfrom the reactor product.

11. The instrument of paragraph 1 further comprising an AC signalprocessing element effective for noise rejection/filtering and signalamplitude measurements.

12. The instrument of paragraph 1 further comprising anelectronic/computer automated control system.

13. An analytical instrument comprising: a sample-handling unitcomprising multiple valves and a syringe connected through a three-wayvalve to both a coil of tubing and a reservoir containing low-TOCdilution water, wherein the volume of the coil is at least as large asthe volume of the syringe; a pump component effective to draw samplefrom a sample source and deliver it by a conduit connection to a fluidinterconnection element; a mixing/sparging chamber connected to the coilof tubing, said chamber including a sparging element for spargingCO₂-free gas through a solution/suspension in the chamber; a source ofcompressed CO₂-free gas connected to the sparging element and a gascontrol module to control the flow and pressure of such gas; a pumpcomponent and associated conduit to transfer at least a portion of thesolution/suspension from the mixing/sparging chamber to a sealablereactor; a heater and a fan associated with the reactor; a source ofcarrier gas connected to the reactor; a conduit downstream of thereactor carrying the reactor product sequentially through a gas/liquidseparator, an in-line filter, and then to a CO₂ detector; and anassociated automated control system comprising electrical connectionsand operational software adapted to operate fluid valves and othersystem control elements according to a predetermined sequence and/ortiming or, alternatively, in accordance with feedback received fromvarious system monitors.

14. The instrument of paragraph 13 further comprising a valve and aconduit for carrying sparge gas emerging from the mixing/spargingchamber through the gas/liquid separator to the CO₂ detector.

15. An analytical method comprising the following sequential steps:drawing a known volume of sample into a sample-handling portion of ananalytical system; adding suitable volumes of one or more chemicalreagents relative to the volume of sample; mixing the sample andchemical reagents to form a substantially homogenous solution orsuspension; transferring a portion of the homogenous solution/suspensionto a reactor; sealing the reactor; treating the solution/suspension inthe sealed reactor to form a reactor product; bringing the reactor andthe reactor products to about ambient temperature; opening the reactorand, using a stream of carrier gas, transferring the liquid and gaseousreactor products from the reactor to a gas/liquid separator; separatingthe liquid reactor product from the gaseous reactor product; flowing thegaseous reactor product from the gas/liquid separator to a chemicaldetector; and, measuring a chemical component in the gaseous reactorproduct using the detector.

16. The method of paragraph 15 wherein the chemical reagents areselected from acid and oxidizer.

17. The method of paragraph 15 further including the step of addingdilution water to the sample and chemical reagents.

18. The method of paragraph 15 wherein the step of mixing the sample andchemical reagents also includes simultaneously sparging thesolution/suspension with a sparge gas.

19. The method of paragraph 18 further comprising the step of monitoringthe progress of the sparging step by flowing the sparge gas from themixing/sparging step to the chemical detector for analysis.

20. The method of paragraph 15 wherein the solution/suspension includesorganic materials and is heated in the reactor to a temperature betweenabout 150° C. to about 650° C. in the reactor step substantially tooxidize the organic materials.

21. The method of paragraph 15 wherein the solution/suspension is heatedto supercritical fluid temperature/pressure conditions in the reactorstep.

22. The method of paragraph 15 wherein the solution/suspension is heatedto a temperature of about 100° C. or less in the reactor step.

23. The method of paragraph 15 wherein the chemical detector is specificto a material selected from carbon, nitrogen and sulfur oxidationproducts.

24. The method of paragraph 15 wherein the chemical detector is a CO₂detector.

25. The method of paragraph 15 wherein the chemical detector is anon-dispersive infrared (NDIR) detector.

26. The method of paragraph 25 wherein the NDIR includes an opticalfilter specific to the wavelength of IR radiation absorbed by thechemical component to be measured.

27. The method of paragraph 26 wherein the optical filter is specific toCO₂.

28. The method of paragraph 15 further wherein an AC signal processingelement is used for noise rejection/filtering and signal amplitudemeasurements.

29. The method of paragraph 15 further wherein the analysis is automatedby an electronic/computer automation control system.

30. The method of paragraph 15 further comprising the step ofdetermining a concentration of a chemical component in the sample usinga mathematical formula to correlate a response of the chemical detectorto the gaseous reactor product with the concentration of the chemicalcomponent.

31. Apparatus for treating an aqueous sample containing organic materialcomprising:

-   -   (a) a reactor having reactor inlet and outlet ports and a        reactor interior for containing an aqueous sample under        above-ambient temperature and pressure conditions;    -   (b) high-pressure fluid reactor valve members at said reactor        inlet and outlet ports, said reactor valve members allowing        fluid flow respectively into or out of the reactor interior when        in an open-valve mode or, alternatively, sealing the reactor        interior when in a closed-valve mode;    -   (c) a reactor heater system adapted for rapidly and cyclically        heating the reactor interior to above-ambient temperature        conditions where an aqueous sample is sealed in the reactor        interior; and,    -   (d) a reactor cooling system adapted for rapidly and cyclically        cooling the reactor interior and an aqueous sample sealed in the        reactor interior following a heating cycle.

32. The apparatus of paragraph 31 wherein the reactor heating system isable to heat the reactor interior and an aqueous sample sealed in thereactor interior to a temperature of about 150° C. to about 650° C.,while the reactor interior and the reactor valve members maintain thesample under sealed conditions.

33. The apparatus of paragraph 31 wherein the reactor heating system isable to heat the reactor interior and an aqueous sample sealed in thereactor interior to temperature and pressure high enough to generatesupercritical fluid conditions inside the reactor interior, while thereactor interior and the reactor valve members maintain the sample undersealed conditions.

34. The apparatus of paragraph 31 wherein each of the reactor valvemembers comprises a valve housing having a main fluid inlet and a mainfluid outlet, a moveable valve plunger element inside the valve housing,a front portion of the valve plunger element comprising a polymeric orelastic plunger seal member having a section sized and shaped to matewith and plug the main fluid outlet when the valve plunger element is inan advanced position, and to unseal the main fluid outlet when the valveplunger element is in a retracted position.

35. The apparatus of paragraph 34, the valve member further comprising amotor for alternately advancing or retracting the valve plunger element.

36. The apparatus of paragraph 34, the valve housing further comprisinga purge gas inlet and a purge gas outlet whereby a purge gas can beflowed through the interior of the valve housing while the valve plungerelement is sealing the main fluid outlet.

37. The apparatus of paragraph 31 wherein the reactor heater systemcomprises a hollow tubular heating element with the reactor in thehollow interior of the heating element.

38. The apparatus of paragraph 31 wherein the reactor cooling systemcomprises a fan located proximate to the reactor and oriented to blowambient air along the exterior of the reactor.

39. The apparatus of paragraph 37 wherein the tubular heating element isopen at each end, and further wherein the reactor cooling systemcomprises a fan located proximate to one open end of the heating elementand oriented to blow ambient air through the hollow interior of theheating element and along the exterior of the reactor.

40. Apparatus for mixing an aqueous sample containing particulatematerial with one or more other liquid components, said apparatuscomprising:

-   -   (a) a sealed tubular mixing container having a liquid inlet/gas        outlet section at a first container end, said liquid inlet/gas        outlet section including a sample inlet and a sparge gas outlet;        a liquid outlet/gas inlet section at a second container end,        said liquid outlet/gas inlet section including a sparge gas        inlet and a sample outlet; and, between said liquid inlet/gas        outlet section and said liquid outlet/gas inlet section, a fluid        mixing region;    -   (b) a magnetically activatable stirrer element inside said fluid        mixing region;    -   (c) an annular solenoid coil surrounding at least a portion of        said fluid mixing region, said solenoid coil being activatable        by a series of electric current pulses to move the stirrer        element inside the fluid mixing region; and,    -   (d) a porous gas disperser located between the sparge gas inlet        and the fluid mixing region.

41. The apparatus of paragraph 40 wherein the stirrer element is coatedwith a corrosion-resistant outer layer.

42. The apparatus of paragraph 40 wherein the gas disperser has gaspores with a pore size ranging from about 1 μm to about 0.125 in.

43. The apparatus of paragraph 40 wherein the stirrer element isactivatable independently of whether sparge gas is being supplied to thefluid mixing region.

44. A purgeable fluid sealing valve apparatus comprising:

-   -   (a) a valve housing having a main fluid inlet and a main fluid        outlet;    -   (b) a moveable plunger element inside the valve housing, a front        portion of the valve plunger element comprising a plunger seal        member sized and shaped to be seated on and plug the main fluid        outlet when the valve plunger element is in an advanced        position, and to unseal the main fluid outlet when the plunger        is in a retracted position; and,    -   (c) the valve housing further comprising a valve purge gas inlet        and a valve purge gas outlet whereby a purge gas can be flowed        through the interior of the valve housing while the valve        plunger element is sealing the main fluid outlet.

45. The fluid sealing valve apparatus of paragraph 44 wherein saidplunger seal member comprises a polymeric or elastic member.

46. The fluid sealing valve apparatus of paragraph 44 further wherein anexterior wall of the valve plunger element is adapted to seat one ormore O-ring seals.

47. The fluid sealing valve apparatus of paragraph 44 further comprisinga conduit connection from a source of purge gas to the valve purge gasinlet.

48. The fluid sealing valve apparatus of paragraph 44 further comprisinga motor for alternately advancing or retracting the valve plungerelement.

49. A purgeable non-dispersive infrared (NDIR) detector apparatuscomprising:

-   -   (a) an IR source chamber comprising an IR source chamber purge        gas inlet and a purge gas outlet, and containing an infrared        radiation source;    -   (b) an IR detector chamber comprising an IR detector chamber        purge gas inlet and a purge gas outlet, and containing an        infrared detector; and,    -   (c) between the IR source chamber and the IR detector chamber,        an optical path chamber having an optical chamber gas inlet port        at a first end of the optical path chamber and an optical        chamber gas outlet port at a second end of the optical path        chamber.

50. The NDIR apparatus of paragraph 49 further comprising a firstcompartment separation lens that isolates the IR source chamber from theoptical path chamber, and a second compartment separation lens thatisolates the IR detector chamber from the optical path chamber.

51. The NDIR apparatus of paragraph 49 further comprising an opticalfilter mounted in the infrared detector in front of the sensing elementof the detector.

52. The NDIR apparatus of paragraph 51 wherein the optical filter is a4.26 μm±0.2 μm filter.

53. The NDIR apparatus of paragraph 49 further comprising an electroniccontrol system for automating operation of the apparatus, comprising:

-   -   (a) a driver to actuate the IR source at the modulation        frequency;    -   (b) a bandpass filter to pass the infrared detector signal        content at the modulation frequency;    -   (c) an analog-to-digital converter to sample the output of the        bandpass filter many times during each modulation cycle; and,    -   (d) digital signal processing elements to further bandpass        filter the samples from the analog-to-digital converter, and to        calculate the amplitude of the resulting AC signal.

54. The NDIR apparatus of paragraph 49 further comprising an electroniccontrol system for automating operation of the apparatus.

55. The NDIR apparatus of paragraph 49 further comprising conduitconnections from a source of purge gas to the IR source chamber purgegas inlet and to the IR detector chamber purge gas inlet.

56. The NDIR apparatus of paragraph 49 wherein the IR source comprises amodulated, thin-film IR radiator.

57. The NDIR apparatus of paragraph wherein the IR, detector comprises apyroelectric, lithium tantalate sensor element.

58. A sample/reagent handling apparatus comprising:

-   -   (a) separate sources of one or more liquids selected from an        aqueous solution/suspension containing at least an impurity,        dilution water, oxidizing reagent, and acid;    -   (b) conduit connections between the sources of the aqueous        solution/suspension, oxidizing reagent and acid and a first end        of a length of holding tubing, and a dilution water conduit        connection between the dilution water source and a second end of        the tubing;    -   (c) a calibrated syringe in fluid communication with the        dilution water conduit connection, the syringe having an        internal volume that is equal to or less than the internal        volume of the tubing;    -   (d) a conduit connection between the first end of the tubing and        a mixing device; and,    -   (e) fluid valves along each of the conduit connections such that        the syringe can be used to separately draw measured volumes of        oxidizing reagent, acid and aqueous solution/suspension into the        first end of the tubing by drawing dilution water from the        second end of the tubing into the syringe, followed by        discharging the dilution water in the syringe back into the        second end of the tubing in order to transfer the liquids held        in the first end of the tubing to the mixing device.

59. The sample/reagent handling apparatus of paragraph 58 furthercomprising a multi-way fluid hub located along the conduit connectionsbetween the aqueous solution/suspension, oxidizing reagent and acidsources and the first end of the tubing.

60. The sample/reagent handling apparatus of paragraph 58 wherein themixing device comprises a mixing chamber in which the liquidstransferred from the first end of the tubing can be mixed, or spargedwith sparge gas, or mixed and sparged simultaneously.

61. The sample/reagent handling apparatus of paragraph 60 wherein themixing device comprises:

-   -   (a) a sealed tubular mixing container having a liquid inlet/gas        outlet section at a first container end, said liquid inlet/gas        outlet section including a sample/reagent inlet and a sparge gas        outlet; a liquid outlet/gas inlet section at a second container        end, said liquid outlet/gas inlet section including a sparge gas        inlet and a sample mixture outlet; and, between said liquid        inlet/gas outlet section and said liquid outlet/gas inlet        section, a fluid mixing region;    -   (b) a magnetically activatable stirrer element inside said fluid        mixing region;    -   (c) an annular solenoid coil surrounding at least a portion of        said fluid mixing region, said solenoid coil being activatable        by a series of electric current pulses to move the stirrer        element inside the fluid mixing region; and,    -   (d) a porous gas disperser located between the sparge gas inlet        and the fluid mixing region.

62. Liquid treatment apparatus for treating an aqueous sample containinga non-aqueous component to prepare the sample for a measurement of thenon-aqueous component, said apparatus comprising a sample/reagenthandling apparatus according to paragraph 61 in combination with areactor apparatus comprising:

-   -   (a) a reactor having reactor inlet and outlet ports and a        reactor interior for containing an aqueous sample under        above-ambient temperature and pressure conditions;    -   (b) high-pressure fluid reactor valve members at said reactor        inlet and outlet ports, said reactor valve members allowing        fluid flow respectively into or out of the reactor interior when        in an open-valve mode or, alternatively, sealing the reactor        interior when in a closed-valve mode;    -   (c) a reactor heater system adapted for rapidly and cyclically        heating the reactor interior to above-ambient temperature        conditions where an aqueous sample is sealed in the reactor        interior;    -   (d) a reactor cooling system adapted for rapidly and cyclically        cooling the reactor interior and an aqueous sample sealed in the        reactor interior following a heating cycle; and,    -   (e) a mixing device/reactor conduit connection between the        sample mixture outlet of said mixing device and the fluid        reactor valve member at said reactor inlet port.

63. Analytical apparatus for measuring a non-aqueous component of anaqueous sample wherein at least a portion of the non-aqueous componentmay be present in the form of an organic material, said apparatuscomprising a liquid treatment apparatus according to paragraph 62 incombination with a non-dispersive infrared (NDIR) detector apparatuscomprising:

-   -   (a) an IR source chamber comprising an IR source chamber purge        gas inlet and a purge gas outlet, and containing an infrared        radiation source;    -   (b) an IR detector chamber comprising an IR detector chamber        purge gas inlet and a purge gas outlet, and containing an        infrared detector;    -   (c) between the IR source chamber and the IR detector chamber,        an optical path chamber having an optical chamber gas inlet port        at a first end of the optical path chamber and an optical        chamber gas outlet port at a second end of the optical path        chamber; and,    -   (d) a reactor/NDIR conduit connection between the fluid reactor        valve member at said reactor outlet port and the optical chamber        gas inlet port of the NDIR detector.

64. The analytical apparatus of paragraph 63 further comprising agas/liquid separator along the reactor/NDIR conduit connection to removeliquid components of the product of the reactor prior to reaching theNDIR.

65. The analytical apparatus of paragraph 63 further comprising a gassupply system that provides CO₂-free carrier gas to the reactor totransport reactor gas products along the reactor/NDIR conduit to theNDIR.

66. The analytical apparatus of paragraph 65 wherein each of the fluidreactor valve members comprise:

-   -   (a) a valve housing having a main fluid inlet and a main fluid        outlet;    -   (b) a moveable plunger element inside the valve housing, a front        portion of the valve plunger element comprising a plunger seal        member sized and shaped to be seated on and plug the main fluid        outlet when the valve plunger element is in an advanced        position, and to unseal the main fluid outlet when the plunger        is in a retracted position; and,    -   (c) the valve housing further comprising a valve purge gas inlet        and a valve purge gas outlet whereby a purge gas can be flowed        through the interior of the valve housing while the valve        plunger element is sealing the main fluid outlet; and, further        wherein there is a conduit connection from the gas supply system        to the valve purge gas inlet.

67. The analytical apparatus of paragraph 66 wherein there are conduitconnections between the gas supply system and the IR source chamberpurge gas inlet and the IR detector chamber purge gas inlet.

68. A method for treating an aqueous sample containing organic material,the method comprising the steps of:

-   -   (a) mixing a known volume of the aqueous sample with one or more        other liquids selected from oxidizer, acid and dilution water to        form a sample mixture;    -   (b) flowing at least a portion of the sample mixture into the        interior of a reaction vessel which is at substantially ambient        conditions, said reactor vessel being adapted to be alternately        and repeatedly opened and sealed at reactor inlet and outlet        ports;    -   (c) sealing the portion of sample mixture in the interior of the        reaction vessel;    -   (d) rapidly heating the interior of the reaction vessel and the        sample mixture portion inside to temperature and pressure        substantially above ambient conditions and for a time sufficient        substantially to oxidize the organic material and form a reactor        product;    -   (e) stopping the heating step and then rapidly cooling the        interior of the reaction vessel and the reactor product inside        to substantially ambient conditions to form cooled liquid and        gaseous reactor products; and,    -   (f) opening the reaction vessel and removing the cooled liquid        and gaseous reactor products from the reactor interior.

69. The method of paragraph 68 wherein the reactor interior is heated toa temperature between about 150° C. to about 650° C. in step (d).

70. The method of paragraph 68 wherein the reactor interior is heated totemperature and pressure high enough to generate supercritical fluidconditions in step (d).

71. The method of paragraph 68 wherein the reactor interior is heated toa temperature of about 100° C. or less in step (d).

72. The method of paragraph 68 wherein the reaction vessel is positionedin the hollow interior of a tubular heating element which is turned onto effect the heating step (d).

73. The method of paragraph 68 wherein the heating step (d) is completedin about 30 minutes or less.

74. The method of paragraph 68 wherein the heating step (d) is completedin about 4 minutes or less

75. The method of paragraph 68 wherein the reaction vessel is cooled incooling step (e) by blowing ambient air over the exterior of thereaction vessel.

76. The method of paragraph 68 wherein the reaction vessel is sealed instep (c) by closing purgeable high-pressure reactor valves at thereactor inlet and outlet ports, the method additionally comprising thestep of flowing a CO₂-free purge gas through the respective interiors ofthe reactor valves while the reaction vessel is sealed.

77. The method of paragraph 68 further comprising the step of flowingCO₂-free carrier gas through the interior of the reaction vessel as apart of step (f).

78. A method for treating the combination of an aqueous samplecontaining particulate material and one or more other liquid componentsto form a substantially homogeneous and, optionally, gas-free liquidmixture, the method comprising the steps of

-   -   (a) introducing the aqueous sample containing particulate        material and the other liquid components into a mixing chamber        having a liquid inlet and outlet, a gas inlet and outlet, and        containing a magnetically activated stirring member;    -   (b) activating the stirring member to move inside the mixing        chamber and to agitate the liquid contents and form a sample        mixture; and,    -   (c) if the removal of gases from the sample mixture is desired,        introducing a substantially CO₂-free sparge gas to a lower        portion of the mixing chamber simultaneously with activation of        the stirring member.

79. The method of paragraph 78 wherein the other liquid components areselected from oxidizing reagent, acid and diluting water.

80. The method of paragraph 78 wherein the stirring member is activatedby passing a series of current pulses through an annularly disposedsolenoid coil surrounding the mixing chamber.

81. The method of paragraph 78 wherein the sparge gas is introduced intothe mixing chamber through a porous gas disperser.

82. The method of paragraph 81 wherein the porous gas disperser haspores with a pore diameter of about 1 μm to 0.125 in.

83. The method of paragraph 79 wherein step (c) is carried out for aperiod of about 10 seconds to 20 minutes at a sparge gas flow rate ofabout 50 to 500 cc/min.

84. A method for measuring a chemical component of a fluid streamcomprising the steps of

-   -   (a) providing a non-dispersive infrared (NDIR) detector        apparatus comprising:        -   (i) a sealed IR source chamber comprising an IR source            chamber purge gas inlet and a purge gas outlet, and            containing an infrared radiation source;        -   (ii) a sealed IR detector chamber comprising an IR detector            chamber purge gas inlet and a purge gas outlet, and            containing an infrared detector; and,        -   (iii) between the IR source chamber and the IR detector            chamber, a sealed optical path chamber having an optical            chamber fluid inlet port at a first end of the optical path            chamber and an optical chamber fluid outlet port at a second            end of the optical path chamber;    -   (b) flowing a fluid stream containing the chemical component        into the inlet port, through the optical chamber, and out        through the outlet port, while IR radiation is being directed        through the optical chamber;    -   (c) throughout step (b), flowing a purge gas that is        substantially free of the chemical component being measured        through the IR source chamber and the IR detector chamber;    -   (d) modulating the intensity of the IR radiation directed        through the optical chamber; and,    -   (e) based on the detection response of the chemical detector to        the passage of the fluid stream through the optical chamber,        calculating a concentration of the chemical component using a        mathematical correlation formula.

85. The method of paragraph 84 wherein the NDIR includes an opticalfilter that filters IR radiation at wavelengths other than thewavelength that is absorbed by the chemical component.

86. The method of paragraph 85 wherein the chemical component is CO₂ andthe optical filter is a 4.26 μm±0.2 μm optical filter.

87. The method of paragraph 84 wherein step (e) is based either on adetermination of peak absorbance of the IR radiation by the chemicalcomponent in the fluid stream flowing through the optical chamber or bydetermining the area of the complete response curve generated by passingthe fluid stream through the optical chamber.

88. The method of paragraph 84 further comprising the steps ofautomating the NDIR detection and measurement sequence with anelectronic/computer control system comprising:

-   -   (a) a driver to actuate the IR source at the modulation        frequency;    -   (b) a bandpass filter to pass the infrared detector signal        content at the modulation frequency, while rejecting DC offset,        noise, and harmonics of the modulation frequency;    -   (c) an analog-to-digital converter to sample the output of the        bandpass filter many times during each modulation cycle; and,    -   (d) digital signal processing elements to further bandpass        filter the samples from the analog-to-digital converter to        reject noise while passing the signal at the modulation        frequency, and to calculate the amplitude of the resulting AC        signal.

89. The method of paragraph 84 further comprising the steps ofautomating the NDIR detection and measurement sequence with anelectronic/computer control system.

90. A method for introducing measured volumes of an aqueous sample andone or more other liquids into an analytical instrument using a singlemeasurement syringe without contaminating the syringe with the sample orthe other liquids, said method comprising the steps of:

-   -   (a) providing a sample/reagent handling system comprising:        -   (i) separate sources of one or more liquids selected from an            aqueous solution/suspension, dilution water, and one or more            reagents;        -   (ii) conduit connections between the sources of the aqueous            solution/suspension and the reagents and a first end of a            length of holding tubing, and a dilution water conduit            connection between the dilution water source and a second            end of the tubing;        -   (iii) a calibrated syringe in fluid communication with the            dilution water conduit connection, the syringe having an            internal volume that is less than or equal to the internal            volume of the tubing; and,        -   (iv) fluid valves along each of the conduit connections;    -   (b) filling the holding tubing with dilution water;    -   (c) drawing a first measured volume of a first one of the        aqueous sample or the other liquids into the first end of the        tubing by opening and/or closing the appropriate fluid valves        and then opening the syringe to draw the first measured volume        of dilution water into the syringe from the second end of the        tubing;    -   (d) drawing a second measured volume of a second one of the        aqueous sample or the other liquids into the first end of the        tubing by opening and/or closing the appropriate fluid valves        and then additionally opening the syringe to draw the second        measured volume of dilution water into the syringe from the        second end of the tubing; and,    -   (e) transferring the first measured volume of the first one of        the liquids and the second measured volume of the second one of        the liquids to a mixing location by opening and/or closing the        appropriate fluid valves and then closing the syringe to fully        discharge all of the dilution water in the syringe back into the        second end of the tubing thereby driving the liquids in the        first end of the tubing out of the tubing.

91. The method of paragraph 90 further comprising the step between steps(d) and (e) of drawing a third measured volume of a third one of theaqueous sample or the other liquids into the first end of the tubing byopening and for closing the appropriate fluid valves and thenadditionally opening the syringe to draw the third measured volume ofdilution water into the syringe from the second end of the tubing.

92. The method of paragraph 90 wherein the holding tubing is coiled tooccupy a smaller space.

93. The method of paragraph 90 further wherein the sample/reagenthandling system includes a multi-way fluid hub located along the conduitconnections between the liquid sources and the first end of the tubing.

94. An analytical method comprising the steps of:

-   -   (a) introducing measured volumes of an aqueous sample and one or        more other liquids into an analytical apparatus according to the        method of paragraph 90;    -   (b) transferring the measured volumes of liquids from the first        end of the holding tube to a mixing location where the liquids        are thoroughly mixed and, optionally, can also be sparged to        form a sample mixture;    -   (c) flowing at least a portion of the sample mixture to a        sealable reaction vessel, and treating the sample mixture by the        steps of:        -   (i) sealing the portion of sample mixture in the interior of            the reaction vessel;        -   (ii) rapidly heating the interior of the reaction vessel and            the sample mixture portion inside to temperature and            pressure substantially above ambient conditions and for a            time sufficient substantially to oxidize the organic            material and form a reactor product;        -   (iii) stopping the heating step and then rapidly cooling the            interior of the reaction vessel and the reactor product            inside to substantially ambient conditions to form cooled            liquid and gaseous reactor products; and,        -   (iv) opening the reaction vessel and removing the cooled            liquid and gaseous reactor products from the reactor            interior; and,    -   (d) transferring at least the gaseous reactor product to a        chemical detector and measuring a chemical component of the        gaseous reactor product using the detector.

95. The method of paragraph 94 further including the step of treatingthe reactor product in a gas/liquid separator to remove the liquidreactor product before sending the gaseous reactor product to thechemical detector.

96. The method of paragraph 94 further wherein the chemical detector isa non-dispersive infrared (NDIR) detector.

These and other specific method and apparatus embodiments of thisinvention will be better understood in connection with the followingdetailed invention description and the several drawings in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 (Block Diagram) is a diagram showing in block form the five keyfluidic sub-assemblies of a preferred embodiment of a measurementapparatus according to this invention.

FIG. 2 (Fluidics Schematic) is an overall schematic of the functionalcomponents of a measurement apparatus according to this inventionshowing in detail the several component elements that comprise each ofthe several fluidic sub-assemblies as illustrated in FIG. 1.

FIG. 3 (Sparger With Mixing Function) is a schematic, partiallycut-away/sectional view of a mixer/sparger component in accordance withthis invention.

FIG. 4 (High-Pressure Valve) is a schematic, partiallycut-away/sectional view of a high-pressure reactor valve used to sealthe reactor in accordance with this invention.

FIG. 5 (Reactor Assembly) is a schematic, partially cut-away/sectionalview of a reactor sub-assembly in accordance with this invention.

FIG. 6 (NDIR Optical Bench) is a schematic, partially cut-away/sectionalview of an NDIR sub-assembly in accordance with this invention.

FIG. 7 (Block Diagram of NDIR Detector) is a block diagram illustratinginternal details and related electrical connections and components of anNDIR sub-assembly as illustrated in FIG. 6.

FIG. 8 (Response to CO₂) is a graph illustrating a typical response of aNDIR detector in accordance with this invention to CO₂ contained in agaseous reactor product produced in the instrument by oxidation oforganic compounds.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

FIG. 1 is a block schematic of one preferred embodiment of an automatedcarbon measurement apparatus/analyzer according to this inventionillustrating the five component sub-assemblies 1 to 5 that comprise theanalyzer. As illustrated in FIG. 1, an aqueous sample is drawn into asample-handling sub-assembly 1 of the apparatus, where the desiredvolumes of acid reagent and/or oxidizer reagent are added to a selectedvolume of sample. The sample may also be diluted at this stage withlow-TOC dilution water if necessary before being passed to reactorsub-assembly 3.

The sample, reagents and dilution water if any are mixed in thesample-handling portions of the apparatus to create a sample mixturecomprising a substantially homogenous solution or suspension. If NPOC isto be measured, the acidified sample mixture also is sparged withCO₂-free gas provided by the gas control sub-assembly/module 2. The flowrate of the sparge gas is controlled to ensure that IC in the sample isremoved efficiently and substantially completely. If TC or IC is to bemeasured, the sample mixture is mixed but not sparged.

A portion of the homogenous solution/suspension is then transferred tothe reactor sub-assembly 3. If NPOC or TC is to be measured, thesolution/suspension containing oxidizer is heated in a sealed reactor tooxidize the organic compounds in the solution/suspension, and then it iscooled to near room temperature. If IC is to be measured, oxidizer isnot added to the solution/suspension. In this case, thesolution/suspension may be warmed to facilitate conversion ofbicarbonates and carbonates to CO₂, but it is not heated so much thatoxidation of organic compounds occurs.

Next, a stream of carrier gas from the gas control assembly/module 2transfers the liquid and gas products in the reactor sub-assembly 3 to agas/liquid separator sub-assembly/module 4. The liquid exits theanalyzer from the gas/liquid separator module 4 while the gas product,containing the CO₂, flows to the NDIR detector sub-assembly 5. After theCO₂ in the gas product is measured, the gas product and carrier gasmixture can be flowed through the gas/liquid separator module 4, andvented to the atmosphere.

FIG. 2 is a schematic showing the several fluidic components of theapparatus in more detail. In FIG. 2, sub-assemblies 1 to 5 as shown inFIG. 1 are delineated by broken lines. The sample-handling sub-assembly1 comprises a syringe 6 that is connected through a three-way valve 7 toa coil of tubing 8 and a dilution water reservoir 9 containing low-TOCdilution water. A representative practice of the invention using theapparatus as illustrated in FIG. 2 is described below. It will beunderstood, however, that alternative sequences and methods forintroducing the sample, reagent(s) and dilution water into the systemcould be used consistent with the scope of this invention. For example,using the apparatus illustrated in FIG. 2, the oxidizer and acidreagents could be moved from coil 8 to a mixing location in theapparatus, such as to mixer/sparger 18, prior to introducing the sampleinto the system in order to maintain a separation between thesecomponents until they are ready to be mixed at the mixing location.

Initially, the syringe is empty, and the valve 7 and coil 8 contain onlydilution water. The volume of coil 8 is designed and selected to be atleast as large as, and preferably larger than, the volume of syringe 6,so the only liquid that can enter the syringe is dilution water fromcoil 8 or reservoir 9. When an analysis begins, valve 10 is open, andvalves 11, 12, and 13 are closed. Syringe 6 starts filling with dilutionwater drawn from a syringe end of coil 8, which causes oxidizer reagentfrom oxidizer reagent reservoir 14 to be drawn through the six-way fluidelement 17 and into a sample/reagent end of coil 8. When syringe 6 hasdrawn the required volume of oxidizer into the sample/reagent end ofcoil 8, syringe 6 stops momentarily and valve 10 closes. Valve 11 opensand syringe 6 draws additional dilution water from the syringe end ofcoil 8 into syringe 6, which in turn draws the required volume of acidfrom acid reservoir 15 into the sample/reagent end of coil 8, where itmay partially mix with the oxidizer reagent already in this end of coil8. When the desired volume of acid has entered coil 8, the syringe 6stops momentarily, valve 11 closes, and valve 12 opens to allow therequired volume of sample to be drawn into the sample/reagent end ofcoil 8, as additional dilution water from the syringe end of coil 8 isdrawn into syringe 6. When the required volume of sample has entered thecoil, syringe 6 stops again, and valve 12 closes. The coil 8 nowcontains the desired volumes of oxidizer, acid, and sample solutionrequired for the measurement. Coil 8 may or may not contain a materialamount of dilution water at this point, depending on the internal volumeof coil 8 relative to the volumes of oxidizer, acid and sample drawninto coil 8, and also depending upon whether or not the sample requiresdilution prior to analysis.

It will be understood that, if the procedure described above took anysignificant amount of time to complete, there would be an opportunityfor oxidizer reagent or, perhaps, even acid, from the sample/reagent endof coil 8 to diffuse into dilution water at the syringe end of coil 8,which could lead to contamination of the syringe. In practice, however,the several steps of filling coil 8 are completed in a sufficientlyshort time that there is no opportunity for reagents drawn into thesample/reagent end of coil 8 to diffuse into the dilution water at thesyringe end of coil 8.

In some cases, the source of the sample is a long distance from theanalyzer, especially when the analyzer of this invention is used tomonitor a process stream of an industrial operation. In such asituation, the analyzer could not provide real-time measurements if theonly way of pumping the sample to the analyzer were the syringe pump.Therefore, in a preferred embodiment of the invention, the apparatusalso includes a pump 16 which can rapidly draw a fresh portion of sampleto the six-way union 17. Once the new sample portion has been deliveredto element 17, it can be drawn into coil 8 quickly by further openingsyringe 6 at the appropriate time.

The next step in the measurement method is to open valve 13. With valve13 open, the step of closing syringe 6 results in moving the liquidsfrom coil 8 to a mixing location in the system, such as to themixer/sparger component 18, where the reagents, sample, and dilutionwater, if any, are thoroughly mixed. Particulate material in the sampleis kept in suspension so that the solution/suspension is substantiallyhomogeneous.

In one alternative and sometimes preferred embodiment, the acid andoxidizer are first drawn into coil 8 and then are transferred intomixing/sparging chamber 18. The sample and dilution water (if any) arethen drawn into coil 8 and transferred into mixing/sparging chamber 18where the sample, acid, oxidizer, and dilution water are mixed.Transferring the liquids to the mixing/sparging chamber 18 in two stepshas the advantage of preventing premature reaction of IC in the samplewith the acidic reagents in coil 8. Generation of gas in coil 8 (fromreaction of IC in the sample with acid) reduces the volume of sampledrawn into coil 8, adversely affecting the accuracy of the measurement.

Mixer/sparger 18 includes a mixing and sparging chamber that also isdesigned to provide for sparging CO₂-free gas through thesolution/suspension to remove IC, if NPOC is to be measured. Forsparging, after the chamber element of mixer/sparger 18 contains thereagents, sample and dilution water (if any), valve 19 opens to allowthe sparge gas to bubble through the chamber element of mixer/sparger18. The gas can be provided from a pressurized gas cylinder (not shown)or from a pump (not shown) that draws ambient air through an absorberthat purifies the air sufficiently for use as a CO₂-free sparge gas,and/or as a carrier gas, and/or as a purge gas. In either case, theCO₂-free gas is prepared for use in gas control sub-assembly module 2.Sub-assembly 2 includes a pressure-regulating device 20 that adjusts thepressure of the gas to about 20 psig. A proportioning valve 21 controlsthe flow rate of the gas flowing through valve 19 by means of a spargegas flow sensor 22. Additionally, a carrier gas flow sensor 23 inanother conduit branch can be used to monitor and control the flow rateof the carrier gas to reactor sub-assembly 3. Additionally, a restrictor24 in still another conduit branch can be used to provide for a smallflow rate of purge gas to the NDIR detector.

In an alternative embodiment, a valve (not shown) can be used to directthe gas that exits the chamber element of mixer/sparger 18 through thegas/liquid separator unit 4 and then to the NDIR sub-assembly 5. Thisarrangement would allow the completeness of the sparging process to bemonitored. Thus, the sparging is considered complete when the NDIRindicates that the concentration of CO₂ in the sparge gas going to theNDIR has decreased to a very small (negligible) value.

When the sparging and/or mixing in the chamber element of mixer/sparger18 is complete, valve 25 opens to allow all or a portion of thesolution/suspension in the chamber element to be drawn into the interiorof reactor 26 by pump 27. High-pressure reactor inlet and outlet valves28 and 29 respectively are open at this point. Valves 30, 31, 32, and 33are closed. The reactor heater 34 is off, and reactor 26 is near ambienttemperature. Pump 27 operates until sufficient liquid from chamber 18has passed through the interior of reactor 26 substantially to rinse outany remaining prior sample and to fill the reactor tube inside reactor26. At this point, pump 27 is stopped, and valves 25, 28, and 29 close.

Reactor valves 28 and 29 are specially designed in accordance with thisinvention to allow the valve housings to be flushed after these valvesare closed. The flushing step removes excess sample that contains CO₂formed by the acidification of the IC in the sample. If this CO₂ werenot flushed out of the valves, it would cause an error in the subsequentmeasurement. To flush the reactor valve housings, valves 30 and 31 areopened, and residual liquid and gases in these housings can then bepumped out by pump 27 and replaced by carrier gas.

After the reactor tube of reactor 26 has been filled with sample andreactor valves 28 and 29 have been flushed, valve 31 closes and valve 32opens to allow carrier gas to flow from sub-assembly 3 through valve 32,pass through the gas/liquid separator 4, and then pass to the NDIRdetector sub-assembly 5. Flow of carrier gas at this time is necessaryto allow the NDIR detector to reach a steady baseline prior to thesubsequent CO₂ measurement. An in-line filter 37 may be provided betweengas/liquid separator 4 and the NDIR unit to prevent aerosols from thereactor 26 and/or from gas/liquid separator 4 from entering the opticalpath 39 of the NDIR detector.

To measure NPOC or TC, the organics contained in the sample portion inthe reactor tube of reactor 26 must be oxidized. This oxidation can bemade to occur by heating the interior of reactor 26 with a heater 34,while controlling the temperature using a temperature sensor 35. Thesealed reactor can be heated, for example, to a temperature betweenabout 150° C. and 650° C. (preferably between about 300° C. and 400° C.,and between about 350° C. and 390° C. in one preferred embodiment). Theheating period may be between about one to thirty minutes, preferablybetween about two and four minutes, and approximately 3 minutes in onepreferred embodiment. During this period, organics are oxidized in thesample portion in the reactor. At the end of that period, heatingelement 34 is turned off, and fan unit 36 is turned on to blow ambientair over reactor 26, cooling it rapidly to near room temperature.Because of the small mass of reactor 26, it is typically cooled by thiscooling step to near ambient temperature in less than about 90 seconds.

To measure IC, the liquid inside reactor 26 is not oxidized. The reactoris filled as described above, but reactor 26 is heated only to atemperature sufficient to facilitate formation of CO₂ from bicarbonatesand carbonates (i.e., typically to no more than about 100° C.). Thesubsequent cooling step may in this case be abbreviated or omittedentirely. Furthermore, the oxidizer reagent is not required for ICmeasurements, and its addition to the sample prior to the reactor stepcan thus be omitted to reduce operating cost and make the analysisfaster.

When the heating and cooling of reactor 26 is completed (or thecomparable IC reactor sequence is completed), valves 30 and 32 close,and valves 28, 29, 31, and 33 open. This apparatus configuration allowscarrier gas to flow through the reactor tube of reactor 26, and carrythe reactor products through gas/liquid separator 4, to the NDIRsub-assembly and along the NDIR optical path 39.

The NDIR measures the absorbance of the CO₂ in the gas flowing alongNDIR optical path 39 at a wavelength of approximately 4.26 μm, e.g.,4.26 μm±0.2 μm. As the CO₂ carried from reactor 26 enters and passesthrough the NDIR, the absorbance measurement begins at a baseline level,rises up to and passes through a maximum level, and then returns to thebaseline level that existed before the valves associated with reactor 26opened. Either the height of the absorbance peak (or the depth of theintensity trough) or the cone-shaped area of the absorbance responsecurve can be calibrated and used to determine the amount of CO₂contained in the gas product coming from the reactor.

The NDIR detector of this invention is comprised of three chambers, asseen in FIGS. 2 and 6. One chamber 38 contains the IR source. Thecentral chamber, which is the NDIR optical path 39, is the chamberthrough which the carrier gas and the gas product from reactor 26 (whichincludes the CO₂) flow. The third chamber 40 contains the IR detector.Chambers 38 and 40 are flushed by CO₂-free gas provided through theconduit that includes flow controller 24 so that CO₂ in the ambient airdoes not affect the measurements made with the NDIR. The NDIR furtherpreferably includes an associated temperature sensor 41 and anassociated pressure sensor 42, proximately located relative to the NDIR,which monitors atmospheric pressure outside the NDIR (which isessentially the same as the pressure of the CO₂ in the NDIR). Thetemperature and pressure measurements made respectively by temperaturesensor 41 and pressure sensor 42 can be used to compensate the responseof the NDIR for variations in the temperature and pressure of the gasbeing measured. Alternatively, sensors 41 and/or 42 may be omitted ifthe measurement does not require temperature and/or pressurecompensation.

One of the several novel components of the apparatus of this inventionis the mixer/sparger 18. As shown in greater detail in FIG. 3, thepreferred mixer/sparger of this invention includes a liquid inlet/gasoutlet section 43, a middle section 44, and a liquid outlet/gas inletsection 45. The top section 43 contains a liquid inlet 43 a and thesparge gas outlet 43 b. The bottom section 45 includes the inlet port 45b for the sparge gas and the outlet 45 a for liquid. The middle section44 includes a chamber element 44 a located inside an annular solenoidcoil 44 b, which is activated by passing a series of current pulsesthrough it. Such current waveform pulsing causes a magnetic stirrer 46positioned inside chamber 44 a to rapidly move up and down insidechamber 44 a. In a preferred embodiment, the magnetic stirrer 46 iscoated with a corrosion-resistant outer layer, and its up-and-downaction under the influence of the solenoid-generated waveform pulsescauses the sample, reagents and dilution water, if any, inside chamber44 a to be rapidly mixed, typically in about 60 seconds or less.

The bottom section 45 of mixer/sparger 18 includes a porous gasdisperser 47, through which sparge gas is directed on its way intochamber 44 a. The pore diameter in the gas disperser 47 may be about 1μm to 0.125 in., e.g., preferably about 5 μm to 50 μm, and about 18 μmin a preferred embodiment. The small bubbles produced by passing thesparge gas through disperser 47 results in efficient removal of IC fromthe liquid in chamber 44 a, generally in about 10 seconds to 20 minutesat sparge gas flow rates ranging from about 50 to about 500 cc/min.,typically and preferably in about one minute or less at a sparge gasflow rate of about 200 cc/min.

Another of the novel components of the apparatus of this invention arethe high-pressure reactor valves 28 and 29 as shown in FIG. 2, and asillustrated in greater detail in FIG. 4. These high-pressure reactorvalves are included in a preferred embodiment of the present invention.As seen in FIG. 4, a polymeric or elastic seal 48 is attached to orcomprises a front end or section of a moveable plunger element 49, whichis designed to move back and forth inside the housing/valve body 50 whenmotor 51 is activated. The rear portion of seal 48 is adapted to retainfirst and second O-rings 52 and 53 respectively, which seal the interiorof housing 50. The front end of seal 48 is sized and shaped to mate withand plug an opening (i.e., an inlet opening or an outlet opening) ofreactor 26 when the valve is closed by advancing plunger element 49.Reactor 26 may be attached to valve housings 50, for example, usingfittings 70 (as seen in FIG. 4), which provide a seal that isessentially leak-free at the pressure produced in reactor 26 when thesolution/suspension is sealed inside reactor 26, and reactor 26 isheated.

Seal 48 is enclosed by a seal chamber defined by the valve housing 50extending from the sealed opening of reactor 26 at least to first O-ring52. This chamber can be continuously or periodically flushed with gasusing seal chamber ports 54 and 55 as shown in FIG. 4. (Reactor valves28 and 29 also each have a third port that is not seen in FIG. 4. Thesample solution/suspension enters or exits the valve and the interior ofreactor 26 through that third port.) This apparatus configuration makesit possible to remove any IC or free CO₂ that may be present in thevalve housing 50 while the sample is being oxidized/treated in reactor26.

FIG. 5 is a schematic illustration of reactor valves 28 and 29 mountedat either end of a reactor 26. In a preferred embodiment, the reactorheater element 34 has a tubular configuration open at both ends andlocated inside a heater housing with the reactor 26 mounted inside thetubular portion of heater 34. In a preferred embodiment, heater 34comprises a thick-film heating element deposited on an electricallyinsulating coating on the tubular portion of heater 34, as shown in FIG.5. The tubular portion of heater 34 may be constructed of stainlesssteel, titanium, or other suitable materials. The two ends of reactor 26pass respectively through slots (not shown in FIG. 5) in the sidewall ofthe tubular portion of heater 34. In a preferred embodiment, reactor 26is a tube constructed of titanium; however, stainless steel, ceramics,and other materials that are sufficiently corrosion-resistant andcompatible with the oxidation temperatures of this invention can beused. As previously discussed, the reactor assembly preferably alsoincludes a fan component to cool the reactor after a heating/oxidationstep. As seen in FIG. 5, the outlet (downstream side) of fan 36 ispreferably positioned close to one open end of the heater 34, and isoriented so that a flow of cooling air during a cooling step passesthrough the heater housing and over both the exterior and interior ofheater 34, and also such that the airflow going through the interior ofthe tubular portion of the heater 34 during a cooling step passes overthe portion of reactor 26 contained within the tubular portion of heater34.

The special NDIR detector sub-assembly 5 of this invention is shown ingreater detail in FIG. 6. The NDIR consists of an optical system and anassociated NDIR electronic system (as illustrated in the block diagramof FIG. 7). The NDIR optical system has three major sections: an IRsource compartment 38, a sample cell/NDIR optical path 39, and an IRdetector compartment 40. Collimating lenses 58 located at either end ofsample cell 39 separate the adjacent sections. In a preferredembodiment, the lenses 58 are constructed of silicon.

In a preferred embodiment, the IR source 56 is a thin-film heater. Itmay be mounted in plates 59 that are attached to an IR source heater andan IR source temperature sensor. Using the associated NDIR electronicsystem, the plates 59 and IR source 56 are controlled to a temperatureof about 65° C. in one preferred embodiment.

In a preferred embodiment, the IR detector 60 is a pyroelectric, lithiumtantalate sensor element. A 4.26 μm filter is mounted in the IR detectorin front of the sensor element. This filter selectively passes infraredradiation at the wavelength that is absorbed by CO₂. Thus, the IRdetector 60 measures the IR radiation that passes through the opticalpath 39 and the filter without being absorbed by CO₂.

The IR detector 60 may be mounted in plates 61 attached to an IRdetector heater and an IR detector temperature sensor. In a preferredembodiment, the IR detector 60 is controlled at a temperature of about55° C. using the associated NDIR electronic system.

Carrier gas and the gas product from reactor 26, including the CO₂, flowthrough the center section 39 of the NDIR. IR source 56 and IR detector60, located in their separate compartments, are isolated from watervapor and potentially corrosive oxidation products by the compartmentseparation lenses 58. The chambers 38 and 40 are also sealed, and CO₂from ambient air is prevented from entering, or at least from remainingin, those chambers by flowing purge gas provided by the gas controlsub-assembly 2. The center section 39 of the NDIR has a gas inlet port62 and a gas outlet port 63, through which the carrier gas and the gasproduct from the reactor, including the CO₂, flow. As illustrated inFIG. 6, the gas inlet port 62 may be located proximate to the IRdetector end of the NDIR, while the gas outlet port 63 is locatedproximate to the IR source end of the NDIR. However, the reverseorientation also is effective.

The electronic system for operating the NDIR sub-assembly in a preferredinvention embodiment is schematically illustrated in FIG. 7. As seen inFIG. 7, the electronic system includes electronic devices selected toprovide power to the IR source, the IR source heater, the IR detector,the IR detector heater, and other electrical components. In a preferredembodiment, the electronics control system modulates the power to the IRsource at a frequency of 55 Hz. Signals may be generated at otherfrequencies for operation of other components, such as the bandpassfilter and analog-to-digital converter, from a field-programmable gatearray (FPGA) as is known in the art.

The FPGA can be adapted or adjusted to generate a 55 Hz clock for the IRsource, with a duty cycle suitable for its operation. The IR sourcedriver converts the logic-level clock signal into the pulsed powerrequired by the IR source. The IR source emits infrared light, modulatedat 55 Hz. This light reaches the IR detector, attenuated by any CO₂present in the center section 39 of the NDIR. The IR detector convertsthe infrared light that it receives back into an electrical signal, withsignal content at 55 Hz that is proportional to the infrared light thatit receives. The detector bandpass filter is selected or adapted toremove harmonics of the 55 Hz signal and DC offset, low-frequency noise,and high-frequency noise generated by the IR detector. A synchronouscircuit, such as a switched-capacitor filter, is used in the detectorbandpass filter, with a clock provided by the FPGA at a multiple of 55Hz. The analog-to-digital converter samples the waveform from thedetector bandpass filter, also using a clock provided by the FPGA at awhole number multiple of 55 Hz. For example, a clock of 5500 Hz provides100 waveform samples per cycle of the IR detector waveform. The FPGA andthe microprocessor perform further bandpass filtering of the digitizedIR detector signal, centered at the modulation frequency of 55 Hz, toremove detector noise and noise from the AC mains at 50 Hz or 60 Hz. Theamplitude of the 55 Hz signal at the output of the digital bandpassfilter is then measured. The response of the IR detector is adjusted fortemperature, pressure, and flow rate as necessary, and the CO₂concentration is calculated in the manner described above. Based on thedescription provided herein, the processing steps described above couldreadily be implemented by one of ordinary skill in this art using anapparatus in accordance with this invention.

FIG. 8 illustrates a typical response curve of an NDIR during a carbonmeasurement sequence. The output is in instrument counts, and the countsare proportional to the amount of IR radiation that strikes the IRdetector 60. When there is no CO₂ in section 39, the response is at itsmaximum or baseline level. As soon as CO₂ enters section 39, theresponse decreases until it reaches a minimum (trough) that correspondsto when the amount of CO₂ in section 39 has reached its maximum (maximumabsorbance). As the CO₂ passes out of section 39, the response returnsto its original baseline level.

There are two ways that the response peak (trough) can be used tocalculate carbon concentrations in an aqueous sample being tested. Theresponse curve can be mathematically integrated, and the resultingcone-shaped area of the response curve can be related to carbonconcentration by one type of mathematical calibration correlation.Alternatively, the height of the peak (depth of the trough) can bemeasured and related to carbon concentration by another type ofmathematical calibration correlation. These mathematical calibrationcorrelations can be developed for a particular instrument according tothis invention by performing tests on samples containing knownconcentrations of IC, OC and/or TC. Basing computations on themeasurement of peak height has the advantage that it is relativelyunaffected by changes in gas flow rate; and, for that reason, this isthe technique used in a preferred embodiment of the present invention.

The present invention has been described in detail with reference topreferred embodiments thereof for illustrative purposes. Althoughspecific terms are employed in describing this invention, they are usedand are to be interpreted in a generic and a descriptive sense only andnot for purpose of limitation. Accordingly, it will be understood tothose of ordinary skill in the art that various changes, substitutionsand alterations in form and details may be made without departing fromthe spirit and scope of the present invention as set forth in thefollowing claims.

1.-57. (canceled)
 58. A sample/reagent handling apparatus comprising:(a) separate sources of one or more liquids selected from an aqueoussolution/suspension containing at least an impurity, dilution water,oxidizing reagent, and acid; (b) conduit connections between the sourcesof the aqueous solution/suspension, oxidizing reagent and acid and afirst end of a length of holding tubing, and a dilution water conduitconnection between the dilution water source and a second end of thetubing; (c) a calibrated syringe in fluid communication with thedilution water conduit connection, the syringe having an internal volumethat is equal to or less than the internal volume of the tubing; (d) aconduit connection between the first end of the tubing and a mixingdevice; and, (e) fluid valves along each of the conduit connections suchthat the syringe can be used to separately draw measured volumes ofoxidizing reagent, acid and aqueous solution/suspension into the firstend of the tubing by drawing dilution water from the second end of thetubing into the syringe, followed by discharging the dilution water inthe syringe back into the second end of the tubing in order to transferthe liquids held in the first end of the tubing to the mixing device.59. The sample/reagent handling apparatus of claim 58 further comprisinga multi-way fluid hub located along the conduit connections between theaqueous solution/suspension, oxidizing reagent and acid sources and thefirst end of the tubing.
 60. The sample/reagent handling apparatus ofclaim 58 wherein the mixing device comprises a mixing chamber in whichthe liquids transferred from the first end of the tubing can be mixed,or sparged with sparge gas, or mixed and sparged simultaneously.
 61. Thesample/reagent handling apparatus of claim 60 wherein the mixing devicecomprises: (a) a sealed tubular mixing container having a liquidinlet/gas outlet section at a first container end, said liquid inlet/gasoutlet section including a sample/reagent inlet and a sparge gas outlet;a liquid outlet/gas inlet section at a second container end, said liquidoutlet/gas inlet section including a sparge gas inlet and a samplemixture outlet; and, between said liquid inlet/gas outlet section andsaid liquid outlet/gas inlet section, a fluid mixing region; (b) amagnetically activatable stirrer element inside said fluid mixingregion; (c) an annular solenoid coil surrounding at least a portion ofsaid fluid mixing region, said solenoid coil being activatable by aseries of electric current pulses to move the stirrer element inside thefluid mixing region; and, (d) a porous gas disperser located between thesparge gas inlet and the fluid mixing region. 62.-96. (canceled)